1. Field of the Invention
The present invention relates to an image projection apparatus such as a liquid crystal projector, and more particularly to an image projection apparatus having a cleaning function of an air filter.
2. Description of the Related Art
The image projection apparatus (Hereinafter, referred to as a projector) as described above is provided with a cooling fan in a chassis in order to cool a light source such as a lamp or an optical modulation element such as a liquid crystal panel. An inlet port that is formed in the chassis to take in outside air as cooling air by the cooling fan is covered with a dust-proof air filter.
The clogging of the air filter caused by dusts may be generated by the use of the projector for a long time. Therefore, the air filter needs to be cleaned regularly or if necessary. Japanese Patent Laid-Open No. 2004-064010 discloses a projector that cleans an air filter by rotating a cooling fan reversely with reference to a normal drive (i.e. at the time of cooling operation) to flow the air in a chassis to an inlet port to blow off the dusts deposited on the air filter.
However, in the projector disclosed in Japanese Patent Laid-Open No. 2004-064010, the cleaning air sprayed on the air filter is air in the chassis. In this case, since the pressure difference is generated between the inside and the outside of the chassis, the cleaning air is inevitably suctioned from the outside of the chassis. Taking the cleaning air from the outside of the chassis is performed via an exhaust port of the cooling air that is provided in the chassis.
Therefore, in order to prevent the dusts from taking in the chassis, an air filter also needs to be provided in the exhaust port of the cooling air.
Moreover, in this projector, a flow path resistance of the air exhausted to the outside of the chassis via the exhaust port during the normal drive increases caused by providing the air filter in the exhaust port of the cooling air, and the necessity of increasing the output of the cooling fan is created or the noise is increased.